on dairy cow performances

Original
Effects of maize and alfalfa
on
JC
article
genotypes
dairy cow performances
Émile
Y Barrière
M Mauries
2
1 Station d’amélioration des
plantes fourragères,
Centre de recherche Inra de Poitou-Charentes, 86600 Lusignan;
2 École
supérieure d’agriculture, 49000 Angers, France
(Received 8 June 1994; accepted
23
February 1995)
Summary — In this trial, we attempted to evaluate the effects of alfalfa and maize genotypes fed to dairy
cows. These genotypes were chosen from records of previous trials with sheep for either their high or
low digestibility. Thirty-two cows were fed a diet based on maize silage ad libitum (M+ or M- genotype)
and alfalfa (A+ or A-) pellets (4.35 kg/day) in a 2 x 2 factorial experiment. Silage intake, milk yield
and composition, body weight and body condition scores were recorded during the 15-week experiment.
The maize genotype of high digestibility (M+) tended to be ingested in larger quantities (14.4 vs
14.0 kg/cow/d) than the other genotype (M-), although showing a lower dry matter content (29.5 vs
31.2%). With this improved genotype, the milk yield was significantly higher (28.1 vs 26.9 kg/cow/day;
P = 0.01) without decreasing effects in the fat and protein content of the milk, but with the cows increasing their body reserves (28.1 kg, P < 0.01No differences were observed in the body condition scores.
The alfalfa effects were not so acute, but the distribution of the improved genotype (A+) improved the
daily milk yield (28.0 vs 27.0 kg/day, P=0.03) and the body condition scores (P=0.04). These principal effects appeared to be additive. The diet built with the best genotypes (M+ A+ diet) provided 2.2
kg milk/cow/day more than with the inferior ones (M- A- diet), displaying a higher body weight gain and
better body conditions, without showing any negative effects on the fat and protein contents. Thus, the
choice of a given genotype (maize or alfalfa in this case) may have strong effect on cow performances.
In the European Union, where each farmer has a milk quota, the choice of an improved maize or
alfalfa
genotype could be essential
dairy cow / feeding
in
limiting production
costs.
value / alfalfa / maize / digestibility
Résumé &mdash; Effets du génotype de maïs et du génotype de luzerne sur les productions laitières.
Dans cet essai, les effets zootechniques de la variabilité génétique pour la valeur alimentaire existant
chez la luzerne et le mais ensilage ont été évalués. Nous avons alimenté des vaches laitières avec de
l’ensilage de maïs distribué ad libitum et des bouchons de luzerne déshydratée et broyée (4,35 kg MS
par vache par jour) dans un essai croisé à quatre modalités (quatre lots de huit animaux) durant 15
semaines. Nous avons utilisé deux génotypes de mais (M+ et M-) et deux génotypes de luzerne (A+
et A-) choisis pour leur digestibilité forte ou faible d’après des études précédentes menées sur moutons. La composition de ces fourrages et leur digestibilité in vivo (DOM) ont été déterminées (tableau
I). Les quantités de fourrages ingérées, les productions laitières (quantité et composition du lait) ainsi
que les variations de poids vifs vides et d’état corporel des animaux ont été enregistrées au long de l’es-
sai. Quel que soit le génotype de luzerne, l’ensilage de mais réalisé avec le génotype de bonne qualité (M+) a permis une production laitière plus élevée (28,1 vs 26,9 kgljour, p 0,01; tableau 11) sans
dégradation des taux butyreux (43,9 vs 43,0 glkg) et protéiques (30,5 vs 29,9 glkg). Les animaux
ayant reçu le maïs (M+) ont repris du poids alors que le poids des autres n’a quasiment pas varié
(+28,1vs 6,5 kg en 98 jours, p < 0,01). Nous n’avons en revanche pas noté de différences d’état corporel. Cet ensilage (M+) a été ingéré en quantité légèrement plus importante que l’ensilage (M ) (14,44
vs 14,0 kgljour, p = 0,07) bien que sa teneur en matière sèche soit plus faible (29,5 vs 3i,2%). Cette
différence d’ingestion ne suffit pas à expliquer les meilleures performances zootechniques des animaux.
Celles ci sont essentiellement dues à un écart important de valeur énergétique entre les deux hybrides.
Par rapport à ces effets nets du génotype de mais, les effets de la luzerne sont plus discrets : les
animaux recevant la luzerne de bonne qualité (A+) ont produit plus de lait (28,0 vs 27,0 kg de lait
brutljour, p = 0,03) avec un état corporel stable (+0,0 vs - 0,2 point, p = 0,04). La composition du lait,
les quantités de maïs ingérées et le poids des animaux n’ont pas été sensibilement modifiés. Les
interactions entre les effets du maïs et ceux de la luzerne ne sont pas significatives (p > 0,45). La
ration constituée des meilleurs génotypes (ration M+A+) a donc permis des performances bien supérieures à celles de la ration (M-A ) bien que ces 2 rations extrêmes aient été ingérées en quantités comparables (21,1kg MSlvacheljour). La production de lait brut a été supérieure de près de 10 % (28,5 vs
26,3 kg par vache et par jour, p < 0,05) sans détérioration des taux butyreux et protéiques (respectivement 43,4 et 30,4 vs 43,2 et 30,1 glkg). Ces performances n’ont pas été réalisées au détriment
des réserves des animaux qui ont repris du poids et amélioré leur état corporel. Ainsi la variabilité
génétique pour la valeur énergétique mise en évidence chez deux espèces de plantes fourragères s’est
traduite par des différences non négligeables de performances zootechniques. À l’heure où la réduction des coûts d’exploitation devient une nécessité pour l’agriculture, l’amélioration génétique de la
qualité des fourrages semble être une voie à ne pas négliger.
=
valeur alimentaire / vache laitière / maïs
ensilage / luzerne
INTRODUCTION
silage (Andrieu
Among the various ways of improving the
quality of forage for ruminants, such as man-
caster et
agement, choice of harvest date or storage,
plant breeding should be one of the most
reasonable ways. It supposes a genetic variability within each given forage species and
useful criteria available for breeders. It is
now well accepted that a genuine genetic
variation for digestibility traits has been found
in some species. This variation has been
detected in the morphological (eg, the leaf to
plant ratio) or chemical composition of forage material or obtained from in vitro or in
vivo experiments. The forage species
involved in in vivo measurements with standard sheep were barley straw (Herbert et
al, 1994), timothy (Mason and Flipot, 1988),
alfalfa (Thomas et al, 1968; Wilson et al,
1978; Émile and Traineau, 1993), corn
and Demarquilly, 1974; Gallais et al, 1976; Deinum et al, 1984; Barrière et al, 1991, 1992) or rapeseed (Lan-
al, 1990; Émile
et
al, 1993b).
Studies involving dairy or fattening cattle
have appeared less frequently. These are,
however, still essential i) because of specific differences between animal species and
their forage utilization, as reported by a
recent review (Dulphy et al, 1994), and ii)
because the specificity of the metabolisms
devoted to meat or milk production must be
taken into account. Studies have shown the
effects of the genotype of maize silage on
milk yield (Barriere and Emile, 1990) or forage intake (Barriere et al, 1995). Similar
experiments have been carried out with cows
fed ad libitum alfalfa green chopped forage
(Emile et al, 1993a, 1995), pointing out in
the same way the effect of alfalfa genotypes
on intake and milk yield. In addition, alfalfa
pellets given with maize silage to high yielding dairy cows may provide an interesting
diet for the production of milk as shown by
Mauries (1991) and Journet (1992).
The objective of this trial was to evaluate
the effects of alfalfa genotypes, as dried pellets, and maize genotypes, as silage, when
given together to dairy cows. Maize silage
and alfalfa genotypes were chosen according to their feeding quality traits, which are
estimates based on previous experiments
with sheep or lactating dairy cows.
MATERIALS AND METHODS
Forage, animal and experimental
design
experiment was conducted at INRA Lusig(France) during the winter 1992-1993. Maize
genotypes were Inra 258 (M+), an old cultivar of
high digestibility, and Rh 162 (M-), a newly registered hybrid with a lower digestibility. Their
digestibilities were, respectively, 72.9% in 36
The
nan
observations and 65.1 % in four observations taken
from our previous trials (Barriere et al, 1992). They
were cropped in the same manner and their harvest dates were carefully chosen in order to obtain
a similar dry matter (DM) content. Alfalfa genotypes were 63-28P (A+), an experimental synthetic with an improved digestibility, and Europe
(A-) as control. In a previous study we found, by
pooling 66 comparisons, that their digestibilities
were, respectively, 67.9 and 65.2% (Emile and
Traineau, 1993). For both cultivars, fresh forage
was chopped in May, June and July (three consecutive cuts), then dried, ground (4.5 mm; Promill
BB48) and pelleted (8 mm diameter).
Among the experimental Holstein herd, 32
mid-lactation cows were blocked into eight groups
of 4 animals, according to the calving date (93 ±
12 d in milk), parity (2 blocks of primiparous cows),
milk yield (32.9 ± 5.7 kg) and body weight (626 +
71 kg). They were then assigned to a 2 x 2 factorial experiment with the two genotypes of maize
silage (M+, M-) and the two genotypes of alfalfa
offered as pellets (A+, A-). Thus, the four experimental treatments were compared using eight
cows for each treatment.
Cows
housed in pens of 8, which were
with individual feeding gates allowing
the evaluation of individual intakes. During a 4week pretrial period, cows were fed a maize silage
diet. They were then allowed 2 weeks to adjust to
the gates. Data recorded during this pretrial period
were used as covariates for the computing of milk
yield and milk composition. For the maize silage
intake, covariates were based on data taken from
the last pretrial week. During the 15 experimental
weeks, cows were fed a diet of maize silage given
ad libitum, 4.4 kg DM alfalfa pellets, 0.14 kg urea,
0.35 kg DM protected soya-rape cakes (Protane
SG - commercial product of CCLP: 1.15 UFL,
391 g PDIN, 385 g PDIE - DM basis) and a premix of minerals and vitamins in accordance with
the requirements (INRA, 1988). Taking into
account the theoretical feeding value of maize
silage and alfalfa and according to the energetic
and nitrogen requirements, this basic diet should
have allowed a daily milk yield of 24.5 or 19.5
kg, respectively, for the multiparous and primiparous cows. The expected milk yields were calculated (with a weekly persistence equal to 97.5
and 98% for the multiparous and primiparous
cows, respectively). Additional concentrates
(Protane 120 - commercial product of CCLP: 1.03
UFL, 138 g PDIN, 138 g PDIE - DM basis) consistent with these expected yields were then given
individually in the milking room (1 kg concentrate/
3 kg milk above those basic levels). The average amount was 1.82 kg DM concentrate/cow/d
during the experiment (from 0.5 to 4.3 kg). The
forage to concentrate ratios were 88:12 when
considering alfalfa pellets as forage.
were
equipped
Measurements and analysis
Throughout
the
experiment, cows were fed at
were daily removed at 07:30.
11:00, and refusals
Diet refusals were recorded 4 day a week. The
amount of maize for each cow was adjusted
daily according to the DM intake of the previous day and in order to ensure a 10% feed
refusal. Alfalfa pellets were given on top of the
maize diet, 2 or 3 times a day, so that refusals
would not occur.
Milkings were at 07:30 and 16:30. Milk samples were taken twice a week from two consecutives milkings and analysed for fat and protein
content. Cows were weighed on two consecutive days at the beginning and at the end of the
trial and twice a month during the experiment.
Empty body weight (EBW) changes were then
calculated according to Chilliard et al (1987).
Body condition (BC) scores were determined by
a visual evaluation each month on a five-point
scale (ITEB, 1984). These evaluations were
always performed by the same person. The
energy balance (feed unit for milk, UFL per animal
per day; 1 UFL = 1.7 Mcal net energy) was calculated by the difference between animal needs
and food supplies: the maintenance, the milk yield
energetic requirements and the negative interactions between forage (maize and alfalfa) and
concentrates were estimated according to
Faverdin et al (1987). The protein balance was
expressed in the same way, with digestible proteins available in the intestine (PDIN and PDIE).
maize i and the block k, the alf alf a j and the block
k; and Eijk is the random error associated with
observation ijk. The body weight and body condition were analysed on variations between the
beginning and the end of the experimental period
using the same model except for the covariate.
Comparisons between the extreme diets (M+A+
and M-A-) were performed using a Bonferonni
test when means were not covariate-adjusted
means. Neither maize x alfalfa interactions nor
maize x block or alfalfa x block were found
(P> 0.45); hence, their effects were pooled into
the error term and only the principal effects are
presented in the tables.
Maize silage and alfalfa pellets digestibilities
measured on six wethers kept in individual
digestibility crates. Three replicates were performed with sheep fed ad libitum on each maize
genotype and 3 on each alfalfa genotype with
sheep kept on maintenance (45 g DM/kg
metabolic weight [MW]). The animals received a
nitrogen and mineral supplement in order to optimize the rumen activity. Daily representative samples of the offered forage and of the faeces were
taken and submitted to a basic chemical analysis
(ashes, crude protein as 6.25 x Kjeldahl nitrogen,
crude fibre using the Weende method; starch
content by the Ewers method). Apparent organic
matter and crude fibre digestibilities (OMD and
CFD) were then recorded and the energy values
computed according to Andrieu and Demarquilly
RESULTS
were
(1987).
The main characteristics of the maize silage
and alfalfa pellets are given in table I. Cow
intake and production traits are listed in table
II and figures 1, 2 and 3.
Feeding value
The OMD of the M+ silage was higher than
that of the M- (70.3 vs 66.1 %, on average,
of the 3 replicates; confidence limit 2.3),
related to a higher CFD (56.9 vs 43.4%;
confidence limit 4.8), and despite a lower
starch content (23.6 vs 28.8%). The A+
genotype had a lower crude fibre content, a
higher protein content and a higher
digestibility (62.2 vs 60.8%; confidence limit
2.3) than the A-genotype.
=
=
Statistical analysis
assessed by an analysis of vari2 x 2 factorial design by the general
linear model procedure of the Statistical Analysis System Institute (1990), using as basic data
the average value of the 15 weeks for each traits.
Concerning the intake, the milk yield and milk
quality, the model was Yijk =p+ !(YPT) + Mi + Aj
+ Ck + MAij + MCik + ACjk + Eijk, where Yijk is
s
the dependent variable for the cow fed the maize
i and the alfalfa j and belonging to the block k; p
is the population mean for the variable; P(YPT) is
the covariates effect (data collected during the
pretrial period); Mi is the effect of maize P, Aj is
the effect of alfalfa; Ck is the effect of the block k;
MAij, MCikand ACjkthe crossed effects between,
respectively, the maize i and the alfalfaj,the
Results
were
ance as a
=
Dry matter intake (DMI)
was high (mean value: 21.1 kg
DM/cow/d) despite the relatively low DM content of silages. No problems were encountered in obtaining a complete consumption of
the pellets (4.35 kg DM/cow/day). Maize DMI
(table II) was slightly reduced in cows fed
M- (14.0 vs 14.4 kg/cow/day; P=0.07),
although DM content was higher (31.2 vs
Total DMI
29.5%). Intakes of maize were not significantly different between the A- and A+ diets
(14.4vs14.1).).
Milk yield and composition
Milk production was higher (P=0.01) with
the M+ diets than with the M- diets (table !i):):
28.1 and 26.9 kg/cow/d, respectively. It was
also greater with A+ diets compared with
A- diets with a difference of 1.0 kg/cow/d
(28.0 vs 27.0%, P = 0.03). Cows fed with a
M+A+ diet produced 2.2 kg/cow/d more than
those fed with a M-A- diet (28.5 vs 26.3 kg,
P < 0.05). Differences appeared in the first
week and were staged throughout the
Body weight and body condition
Body weight variations (EBW) were very
much dependent on the maize genotype
(P < 0.01Cows fed with the M+ genotype
gained an average of 28.1 kg during the
experimental period (average daily gain
[ADG] of 287 g/d in 98 days), while cows
fed with the M- genotype gained only 6.5
kg (ADG 66 g/day). No alfalfa genotype
effect emerged in this trait. The body condition change was significantly influenced
(P 0.04) by the nature of the alfalfa fed.
Animals fed A+ diets maintained their body
=
=
score
while those fed with A- diets lost 0.2
points.
experimental period (fig 1Despite no significant differences, milk fat contents
seemed to be reduced with A+ diets compared with A- diets (-0.5 points) and to be
increased with M+ diets compared with Mdiets (+0.7 points). Fat-corrected milk yield
(4% FCM) and daily fat yield tended to be
higher with M+ diets than with M- diets
(P= 0.03 and P= 0.06, respectively). The
milk protein content was neither influenced
by the maize genotype nor by the alfalfa
one. The effects of maize on the daily protein yields were positive and highly significant
(P< 0.01 ).
Energy balance
According to forage OMD, concentrate composition and diet intake, the energy supplies
of the total diets (table III) increased from
16.6 UFL (diet M-A-) to 18.1 UFL/cow/day
(diet M+A+). The energy balance was
slightly negative for the four diets (-0.9 to
- 0.2 UFL/cow/day). The average nitrogen
content of the diets was 14%. The protein
supplies increased from 1 762 to 1 865 g
PDIN and from 1 713 to 1 812 g PDIE. The
PDI balance decreased from -2 g
(M+A+
diet) to -63 g (M-A+ diet).
DISCUSSION
Forages feeding
value
The diet energy balances were slightly negative. This result is quite amazing as cows
were unlikely to have been kept in underfed
conditions. They gained weight during the
trial, at least cows fed M+ genotype, and
with our feeding management, were able
to react to contingent feeding value differences. Among the different terms involved
in the balance, this may likely be related to
the evaluation of the energy value of the
diet and probably, more specifically, to the
in vivo maize evaluation. By using an evaluation based on the chemical composition
of the forage (protein, crude fibre and starch
according to Dardenne et al, 1993), we
obtained higher OMD values (73.6 and
71.8% for M+ and M-, respectively) which
were consistent in observed performances.
As noted in other experiments, in vivo evaluation with sheep probably underestimated
the energy value, resulting in this case in a
negative balance. Although there was a
large difference (4.2 points) between the
OMD values of the 2 maize genotypes, this
difference was half of what we had
expected. The OMD of the M- genotype
was low (66.1 %) and led to a value of 0.82
UFL. This was nevertheless consistent with
our previous observation (65.1 %; Barribre
et al, 1992) and led to an energy value 10%
lower than the usual value of maize silage
(71% OMD and 0.90 UFL). Cows fed this
genotype reduced their milk production and
stopped to restore body reserves. But for
the M+ genotype, it is surprising that such
a poor value (70.3%) was obtained compared with our previous measures (72.9%
with 36 ± 0.7 samples). This poor value
should not have allowed such production
and body gain levels.
Effects of the maize
genotype
The M+ genotype clearly allowed higher
performances than the M- genotype. We
indeed noted, with any of the alfalfa types,
increase in the milk production (1.1 kg
FCM more) without any decreasing effect
in fat and protein content. The difference in
the energy balance between the two genotypes (+0.8 UFL/d) was in agreement with
the observed difference in the ADG
(+221 g/d). Thus, there was undoubtedly a
maize genotype effect on cow performances. The maize intake (+0.4 kg/cow/d
for the M+ genotype) was not sufficient to
explain such a difference, which should
mainly result from the variations in the
digestibility of these hybrids. The observed
energy value of the two genotypes can be
evaluated by balancing animal requirements
and diet supplies. The M+ genotype had
then an observed energy value of 1.05
UFL/kg DM and the M-, 0.96 UFL. These
high values agreed with evaluations carried
out in other studies involving dairy cows
(Barribre et al, 1995) where the observed
energy value of maize genotypes increased
from 0.85 to 1.12 UFL negatively related to
the amount of concentrates in the diet. The
difference between the two hybrids (0.09
UFL) was in agreement with the difference
highlighted in the in vivo sheep evaluations
in both this study (0.06 UFL) and the previous one (0.11 UFL; Barribre et al, 1992).
Moreover, the marginal efficiency for milk
an
production (kg milk/supplementary UFL)
probably limited by the cows high production level and this might have buffered
was
the true difference between the M+ and M-
genotypes.
The observed variations in hybrid
digestibility were not related to variations in
grain content, that were similar for the two
hybrids (42.5 vs 40.0%). These variations
may relate to variations in lignin content,
and also to variations in phenolic acid content and monomeric composition of lignin
(Argillier et al, 1995a). These variations
could be somehow enhanced because of
the small low grain content of the silage,
but it is also worth noting that Barribre et al
(1990) did not observe differences in dairy
cow performances when fed silage of a 42
and 48% grain content.
Feeding value evaluations with sheep
(OMD and CFD) were consistent with cow
performances, and gave a good ranking of
the genotypes. For breeders, the variations
in digestibility could probably be easily estimated with a trait such as the one proposed
by Argillier et al (1995b), computing, of the
NIRS calibration, the digestibility of the nonstarch and nonsoluble carbohydrates part
of the plant.
These results, pointing out a genetic variation for zootechnical performances, confirm other studies comparing two or more
maize genotypes used as whole plant silage
for feeding high yielding dairy cows (Barriere and Emile, 1990; Barribre et al, 1995).
In those studies, the variation in milk yield
with cows fed a low or high digestible hybrid
neared 1.0 to 2.0 kg/cow/d and body weight
variations were 10 to 30 kg during the
3 months of the experiment.
feeding of
animals with the experimental
alfalfa genotype A+ has a positive influence
on the daily milk yield and on the body condition changes in cows. In previous experiments, but under different feeding conditions, we evidenced stronger positive effects
(fmile et al, 1995) with the same genotypes
given ad libitum as fresh forage without any
other roughage. In the present trial, the percentage of alfalfa in the total diet was only
21 %, lowering its effect. It also appeared
that the dried, ground and pelleted forage
could have a lower feeding value than the
fresh forage, as previously observed by
Demarquilly (1982) or Conrad and Klopfenstein (1988). This depression of digestibility
is related to the fineness of grinding and to
the relatively short time during which forage is exposed to the microflora in the
rumen (Minson, 1990). This depression had
probably also lowered the difference
between the two genotypes, when pellets
were given as the only feed to sheep. Nevertheless, in dairy cattle feeding, the use of
high quality alfalfa pellets is of great interest
(Peyraud et ai, 1994) and this trial shows
that plant breeders need to investigate this
objective further.
As mentioned earlier, the principal effects
(maize and alfalfa) hold concurrently. The
M+A+ diet allowed a higher milk yield (8%
more) and more FCM with a higher protein
content than the M- A- one. Cows fed the
M+A+ diet gained body weight and maintained their body condition scores which is
not the case with cows fed the M-A- diet.
Comparing these two extreme diets, the
marginal efficiency of the energy supplied
was about 1.2 kg of FCM for each extra UFL.
CONCLUSION
Effects of the alfalfa genotype
Compared
effects
to the maize
not so acute.
were
effect, the alfalfa
Nevertheless, the
Genetic variation between maize hybrids for
energy content was first pointed out in sheep
measurements. These results showed that
they could lead to significant variations in
milk yield, milk quality and body weight conditions of the dairy cows. Because our dairy
cattle feeding management was very similar
to that of farmers for high yielding dairy cows,
it is of great interest to note that the choice of
genotype (maize or alfalfa in this case) is of
economical importance in animal rearing. It
could lead to strong variations in animal performances.
For plant breeders, the prediction of the
efficiency of a genotype for dairy cow rearing must include digestibility and ingestibility topics. With a trait such as the one proposed by Argillier et al (1995b), it would be
possible to breed genotypes with a good
cell-wall digestibility and a good grain content. One of the greatest challenges for plant
breeders, regarding maize but also alfalfa,
would probably be the adjustment of a trait
for the intake prediction.
Concurrent measurements by maize
breeders of yield and whole plant digestibility are of agronomic and economic interest,
in providing animal rearers maize hybrids
suitable for all kinds of conditions. As pointed
out by Utz et al (1994), the greatest economic maize breeding traits, at high animal
performance levels, are those related to the
energy content of the plant, rather than
those related to the plant yield. However,
at low animal performance levels, forage
yield appeared as an important economic
trait. These findings are probably not independent of the intake capacity of the animals. These results are probably also true
for other forage species such as alfalfa. In
the European Union, where milk production
is limited by a quota for each farmer, the
choice of a genotype (here, maize silage
and alfalfa) could be the basis towards
reducing production costs.
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